Sensitivity to climate change is believed to be a particular issue for species endemic to mountains on oceanic islands, due to limited migration possibilities and specialised ecology. A significant proportion of island endemics are already at threat. Threatened palm, Hedyscepe canterburyana is endemic to Lord Howe Island, restricted to high altitudes on two mountains into cloud forest; invasive rat predation reduces seedling recruitment. This study investigated the distribution of genetic variation, morphology, growth characteristics, reproductive output and demographic structure of H. canterburyana across an altitude gradient. Demographic surveys determined population structure, reproductive values and development rates; then programmed into stage specific population models to investigate population growth rate at different altitudes. Rat predation impacts on population growth were also examined. Climatic records for Lord Howe Island were examined for climate changes in the last 70 years and if a subsequent range contraction of H. canterburyana has occurred. Microsatellite markers were used to compile the current genetic profile of the species. Significant and unexpected differences in development rate, population structure, reproductive output and population growth rate were identified between altitudes. Despite climatic changes being recorded, there is no evidence of a range contraction. Genetic variation and diversity was moderate and historical gene flow was high, indicating potential adaptive capacity distributed throughout the species range. However, there were low levels of recruitment resulting in significant declines in population size predicted in models. Modelled removal of rat predation reduced this decline, thus rat predation may be the greatest future threat to H. canterburyana.